Broadcast receiver not unregistering

问题

I want to give the user the ability to unregister/register the broadcast receiver with the click of the button.

When the button is pressed for the first time, the broadcast receiver is registered and a toast comes up when the device is connected.

My problem is when I press the button again, the broadcast reciever is not unregistering like I specified.

Can somebody please check if there is something wrong with mylogic, or explain to me if there is another approach to detecting when usb is unplugged/plugged in?

Thank You.

btn.setOnClickListener(new View.OnClickListener() {
            BroadcastReceiver receiver = new BroadcastReceiver() {
                public void onReceive(Context context, Intent intent) {
                    int plugged = intent.getIntExtra(
                            BatteryManager.EXTRA_PLUGGED, -1);
                    if (plugged == BatteryManager.BATTERY_PLUGGED_USB) {
                        Toast.makeText(getApplicationContext(),
                                "Connected to USB", Toast.LENGTH_SHORT).show();

                    }
                    if (plugged != BatteryManager.BATTERY_PLUGGED_USB) {
                        Toast.makeText(getApplicationContext(),
                                "Disconnected from USB", Toast.LENGTH_SHORT)
                                .show();

                    }
                }
            };

            @Override
            public void onClick(View v) {
                int mReceiver = 0;
                mReceiver++;
                if (mReceiver % 2 == 1) {
                    IntentFilter filter = new IntentFilter(
                            Intent.ACTION_BATTERY_CHANGED);
                    registerReceiver(receiver, filter);
                }
                if (mReceiver % 2 == 0) {
                    unregisterReceiver(receiver);
                    Toast.makeText(getApplicationContext(),
                            "Should be unregistered", Toast.LENGTH_LONG).show();
                }

            }
        });

回答1:

Your mReceiver value will always be equal to 1 because of these lines:

            int mReceiver = 0;
            mReceiver++;

I assume that mReceiver is an instance variable, in which case it should just be:

            mReceiver++;

Better still, create a boolean value called isRegistered.

        @Override
        public void onClick(View v) {

            if (!isRegistered) {
                IntentFilter filter = new IntentFilter(
                        Intent.ACTION_BATTERY_CHANGED);

                registerReceiver(receiver, filter);
                isRegistered = true;
            }
            else {
                unregisterReceiver(receiver);
                isRegistered = false;
            }

        }

来源：https://stackoverflow.com/questions/23717933/broadcast-receiver-not-unregistering

标签

android

usb

broadcastreceiver